DESCRIPTION: To date, no vaccine strategy has successfully induced potent broadly neutralizing antibodies (BnAb) against HIV-1. In vitro analysis, passive antibody transfer studies and analysis of antibody responses in the RV144 vaccine efficacy trial suggest non- neutralizing antibodies might contribute to protection against HIV-1 transmission. Three linear regions in the HIV-1 Env MPER, V2 and V3 have been implicated as potential targets of protective non-neutralizing antibody. We have constructed a novel recombinant Lactobacillus acidophilus vaccine platform that is orally delivered and induces antigen-specific mucosal IgA and systemic IgG against MPER peptides inserted into the bacterial surface layer protein. We have developed two different adjuvants for use with recombinant L. acidophilus, IL1? and flagellin (FliC). Specifi Aim 1 will determine the optimal adjuvant for mucosal immunization and whether responses are T-cell dependent or independent. Specific Aim 2 will test whether recombinant Lactobacillus acidophilus expressing candidate MPER, V2, and/or V3 epitopes can induce mucosal and systemic antibody responses that are protective against vaginal HIV-1 challenge in the HLA-DR transgenic (DRAG), humanized mouse model.